mixed flow fan

ABSTRACT

A mixed flow fan having a housing, a stator, and an impeller, with the housing having a downward extending skirt and an upper perimeter as air inlet and a lower perimeter as air exhaust, a central hub with an outer edge, and a plurality of struts connected to the upper perimeter of the skirt and to the outer edge of the central hub. The outer edge of the central hub may be concave or curvilinear or conical. A stator cup which houses the motor is connected to the outer wall of the impeller and to the central hub.

CROSS REFERENCES TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

This disclosure relates to an improvement in mixed flow axial fans, and more particularly to the housing component of the fan, the air inlet of the fan, and the blade configuration of the fan.

Mixed flow fans, as with most fans, have an impeller with a permanent magnet therein and a fixed stator or motor in communication with the impeller to rotate the impeller when power is applied to the stator. The air in a typical mixed flow fan moves down an annulus flowing within the fax structure and around the stator cup located within the housing of the fan. The inlet diameter generally is smaller than the exhaust diameter and, in extreme cases, will be visibly conical. Mixed flow fans improve efficiency over tubaxial fans because, as the air moves in an increasing radius through the conical housing, it builds up a centrifugal component thereby increasing the exhaust pressure.

In this regard, the air exits the exhaust side of the fan at an inclined angle, relative to the axis of rotation of the impeller, thereby preserving the momentum. The internal components of the housing, blade tips, and impeller wall to which the blades are attached, follow the same conical shape as the housing to keep the volume within the annulus comparable along the axis of rotation.

If the annular volume were to increase, diffusion losses reduce the efficiency of the mixed flow effect. The complimentary conical shapes of the housing and impeller components of these typical prior art fans, however, are not without cost. To maintain this complimentary shape, costs to manufacture are significant.

The improved mixed flow fan of this disclosure provides for a cylindrical impeller outer wall onto which the blades are affixed. There is a lateral gap or space between the leading edge of one blade and the trailing edge of the adjacent blade as measured in the direction of rotation. The gap is maintained between all leading edges and trailing edges of all blades. The gap is noticeable when the impeller is viewed planarly; i.e., the impeller being placed on a flat horizontal surface and viewed from above along its axis of rotation. This gap is referred to herein as a planar gap or lateral gap. The planar gap facilitates construction of the impeller and significantly reduces costs for molds.

The improved mixed flow fan of this disclosure employs at least two aspects to overcome the loss of effect from this construction. First, the improved mixed flow fan has a concave or curvilinear or conical shaped hub on the inlet of the housing with a plurality of struts attached to the outer edge of the hub at one end and attached to the outer perimeter of the housing. Unlike struts typically being on the exhaust side of the housing in prior art mixed flow fans, the struts of the improved mixed flow fan are on the inlet side of the housing.

The struts positioned at the inlet side allows the impeller to have a larger diameter. A larger diameter impeller in ths same package allows for much higher volumetric flow compared to fans in the same envelope with impellers located on the air inlet.

Second, impeller blades employ a natural eddy in the shaft region. This eddy replaces or supplements, to a large degree, the conical feature in the outer wall of the impeller. This eddy effect of the improved mixed flow fan creates a small-pressure zone on the exhaust side of the blade. The eddy substitutes the conically-shaped components of the prior art mixed flow fans described above and reduces diffusion losses. In this regard, performance is maintained while production costs are reduced.

The foregoing has outlined some of the more pertinent objects of the improved mixed flow fan. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the improved mixed flow fan. Many other beneficial results can be attained by applying the disclosed improved mixed flow fan in a different manner or by modifying the improved mixed flow fan within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the improved mixed flow fan may be had by referring to the summary of the improved mixed flow fan and the detailed description of the preferred embodiment in addition to the scope of the improved mixed flow fan defined by the claims taken in conjunction with the accompanying drawings.

SUMMARY

The above-noted problems, among others, are overcome by the improved mixed flow fan. Briefly stated, the improved mixed flow fan contemplates a mixed flow fan having a housing, a stator, and an impeller, with the housing having a downward extending skirt with an upper perimeter as air inlet and a lower perimeter as air exhaust, a central hub with an outer edge, and a plurality of struts connected to the upper perimeter of the skirt at a first end and to the outer edge of the central hub at a second end. The outer wall of the impeller has a plurality blades attached. Internal to the outer wall is a stator cup having an inner surface, an outer surface, and a permanent magnet disposed on the inner surface. The stator cup is connected to the outer wall of the impeller and to the central hub.

The outer edge of the central hub may be concave or curvilinear or conical. Each one of the plurality of blades have a leading edge and a trailing edge with a planar gap between each leading edge and each adjacent trailing edge.

The foregoing has outlined the more pertinent and important features of the improved mixed flow fan in order that the detailed description that follows may be better understood so the present contributions to the art may be more fully appreciated. Additional features of the improved mixed flow fan will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and the disclosed specific embodiment may be readily utilized as a basis for modifying or designing other structures and methods for carrying out the same purposes of the improved mixed flow fan. It also should be realized by those skilled in the art that such equivalent constructions and methods do not depart from the spirit and scope of the improved mixed flow fan as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the improved mixed flow fan, reference should be had to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an exploded view of a typical prior art mixed flow fan.

FIG. 2 is an exploded view of the improved mixed flow fan.

FIG. 3, as taken on line 3-3 of FIG. 2, is a top plan view of the housing of the mixed flow fan.

FIG. 4, as taken on line 4-4 of FIG. 3, is a cross-section view of the housing of the mixed flow fan.

FIG. 5, as taken on line 5-5 of FIG. 2, is a plan view of the impeller component of the mixed flow fan.

FIG. 6, as taken on line 6-6 of FIG. 5, is a cross-section view of the impeller component of the mixed flow fan.

FIG. 7 is a detailed view of the top of the shaft from the section of FIG. 6 identified by reference character D.

DETAILED DESCRIPTION

Referring now to the drawings in detail and in particular to FIG. 1, reference character 110 generally designates a prior-art type mixed flow fan. Typically air enters in the direction of Arrow A into the housing through the skirt 112. The impeller 151 rotates about the stator 131 and the stator 131 is fixedly attached to the exhaust component 111 of the housing. As with all impellers, this impeller 151 has a plurality of blades 156, each with a leading edge 155 and a trailing edge 157 and will rotate in the direction of Arrow B.

The central hub 118 is on the exhaust component 111 with struts 116 attached to the central hub 118 and the outer edge of the exhaust component 111. This configuration of the exhaust component 111 defines the housing exhaust openings 126. The outer wall 152 of the impeller 151, as previously described, is conical for the reasons aforementioned.

Reference character 10 of FIG. 2 generally designates the improved type mixed flow fan constructed in accordance with a preferred embodiment thereof. The housing 11 has a downward extending skirt 12 with a central hub 18 having a plurality of struts 16 extending outward from the central hub at one end of the strut and attached to skirt 12 at the other end of the strut 16. An housing inlet opening 26 is defined between one strut 16 and each adjacent strut 16, the outer edge 17 of the central hub 18, and the skirt 12 [FIG. 3 refers].

The stator 31 is directly attached to the inlet component of the improved mixed flow fan of the present disclosure on the underside of the central hub 18 by way of suitable threaded fasteners 25 passing through hub apertures 15 and threaded into stator threaded aperture 35 of the stator 31. A bias member 34 resides below the housing aperture 14 and above the stator 31 the purpose of which is to preload the bearings. Any bias member 34 suited for the intended purpose will suffice. A typical bias member 34 includes, but is not limited to, a compression spring.

The impeller 51 has a plurality of blades 56 connected to its outer wall 52. As with all such blades, each blade 56 has a blade tip 53, a leading edge 55 and a trailing edge 57. Reference now is to FIGS. 1, 5, and 6. Centrally disposed in the impeller 51 is a rotor cup 63 as defined by its inner cup wall 62 and its outer cup wall 64 with a permanent magnet 65 generally disposed on the inner cup wall 62. A shaft 54 is central to the axis of rotation [reference character X] on the impeller 51. Adjacent to the upper end of the shaft 54 is a groove 58 therearound [FIG. 6, reference character D, and FIG. 7 refer].

The blades 56 extend outward radially from the hub 52 and are somewhat angled at their respective tips 53. This is referred to as the “trim line” and is designated by reference character Y as illustrated in FIG. 6. In the preferred embodiment, the downward extending skirt 12 is angled slightly outward, Y, from the axis of rotation X as illustrated in FIG. 4. The blade tips 53, therefore, align with the inner contour of the downward extending skirt 12, i.e., at the trim line Y, leaving a clearance between the blade tips 53 and the inner contour of the downward extending skirt 12 thereby permitting the impeller 51 to rotate freely.

The angle between X and Y generally can range from approximately 5.0° to 15°. As illustrated, and as found best suited for the intended purposes, the angle is approximately 8.6°.

With the inlet housing 11 and its attached stator 31 in place as previously described, the shaft 54 of the impeller 51 inserts through the stator 31, through the bias member 34, and out the housing aperture 14 where it is held thereat by a suitable ring clip 28 which fits securely onto the groove 58 of the shaft 54.

For greater structural integrity of the impeller 51, a plurality of support ribs 66 are positioned in the space defined between the outer wall 52 of the impeller 51 and the outer cup wall 63 of the stator cup 63. Of particular importance to this impeller 51 is the planar or lateral gap 59 between the leading edge 55A of one blade 56A and the trailing edge 57B of the adjacent blade 56B. This planar gap 59 ranges from approximately 2 mm to approximately 10 mm.

The planar gap 59 facilitates the manufacture of the impeller by requiring only a single mold. To increase flow the impeller assembly 51 is located on the air exhaust side and the central hub 18 is located on the air inlet side. Struts 16 and hub 18 create a boundary layer to reduce flow.

Also facilitating the functionality and efficiency of the improved mixed flow fan of the present disclosure is the concave or conical or curvilinear aspect 19 of the outer edge 17 of the central hub 18 as best illustrated in FIG. 4. This illustration of a concave configuration of the central hub 18 allows more inlet air, as compared to a cylindrical hub, by increasing the annulus for air to enter.

The present disclosure includes that contained in the present claims as well as that of the foregoing description. Although this improved mixed flow fan has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and numerous changes in the details of construction and combination and arrangement of parts may be resorted to without departing from the spirit and scope of the improved mixed flow fan. Accordingly, the scope of the improved mixed flow fan should be determined not by the embodiment[s] illustrated, but by the appended claims and their legal equivalents.

Applicant[s] have attempted to disclose all the embodiment[s] of the improved mixed flow fan that could be reasonably foreseen. It must be understood, however, that there may be unforeseeable insubstantial modifications to improved mixed flow fan that remain as equivalents and thereby falling within the scope of the improved mixed flow fan. 

1. A mixed flow fan having a housing, a stator, and an impeller,: said mixed flow fan comprising: (a) said housing having a downward extending skirt with an upper perimeter as air inlet and a lower perimeter as air exhaust, a central hub with an outer edge, and a plurality of struts connected to said upper perimeter of said skirt at a first end and to the outer edge of said central hub at a second end; (b) said impeller having an outer wall with a plurality blades attached thereto and a stator cup with an inner cup wall and an outer cup wall further comprising a permanent magnet disposed on said inner cup wall, said stator cup connected to said outer wall of said impeller; and (c) said stator connected to said central hub.
 2. The mixed flow fan of claim 1 wherein said outer edge of said central hub is curvilinear.
 3. The mixed flow fan of claim 1 wherein said outer edge of said central hub is conical.
 4. The mixed flow fan of claim 1 wherein a diameter of said upper perimeter is smaller than a diameter of said lower perimeter.
 5. The mixed flow fan of claim 1 further comprising a space between said outer cup wall of said stator cup and said outer wall of said impeller.
 6. The mixed flow fan of claim 5 further comprising a plurality of ribs in said space, said ribs attached to said outer cup wall of said stator cup at a first side and attached to said outer wall of said impeller at a second side.
 7. The mixed flow fan of claim 1 wherein said outer wall of said impeller is approximately normal to an axis of rotation of said impeller.
 8. The mixed flow fan of claim 1 further comprising a planar gap between a leading edge of each one of said plurality of blades and a trailing edge of each adjacent one of said plurality of blades.
 9. The mixed flow fan of claim 1 wherein said downward extending skirt bears an angle of between approximately 5.0° to approximately 15.0° to an axis of rotation of said impeller.
 10. The mixed flow fan of claim 9 wherein said downward extending skirt bears an angle of approximately 8.6° to said axis of rotation of said impeller.
 11. The mixed flow fan of claim 9 wherein said blades have a tip bearing an angle of approximately 5.0° to approximately 15.0° from its leading edge to its trailing edge in relation so said axis of rotation of said impeller.
 12. The mixed flow fan of claim 9 wherein said blades have a tip bearing an angle of 8.6° from its leading edge to its trailing edge in relation so said axis of rotation of said impeller. 